1. Field of the Invention
The present invention relates to a wireless communication system, and more particularly, to an apparatus and method for transmitting and receiving signals using a frame structure in a wireless communication system.
2. Discussion of the Related Art
An Institute of Electrical and Electronics Engineers (IEEE) 802.16m system supports both a Frequency Division Duplex (FDD) scheme, including a Half-Frequency Division Duplex (H-FDD) Mobile Station (MS) operation scheme, and a Time Division Duplex (TDD) scheme.
The 802.16m system uses an Orthogonal Frequency Division Multiplex Access (OFDMA) scheme as a multiple access scheme in downlink and uplink.
The following is a brief description of a frame structure of an IEEE 802.16m system which is an exemplary mobile communication system.
FIG. 1 illustrates a basic frame structure in an IEEE 802.16m system.
As shown in FIG. 1, each 20 ms superframe is divided into four 5 ms radio frames having the same size and starts at a SuperFrame Header (SFH). When one of the channel bandwidths of 5 MHz, 10 MHz, and 20 MHz is used, each 5 ms radio frame includes 8 subframes. One subframe may be allocated for downlink or uplink transmission.
The IEEE 802.16m system, which is an exemplary mobile communication system, uses three or more types of subframes. A type-1 subframe includes 6 OFDMA symbols, a type-2 subframe includes 7 OFDMA symbols, a type-3 subframe includes 5 OFDMA symbols.
The basic frame structure is applicable to both the FDD scheme, including the H-FDD MS operation scheme, and the TDD scheme. The number of switching points in each radio frame in the TDD system is 2. The switching points may be defined according to directionality changes from downlink to uplink or from uplink to downlink.
The H-FDD Mobile Station (MS) may be included in an FDD system, and a frame structure for the H-FDD MS is similar to a TDD frame structure. However, in the FDD system, downlink and uplink transmission are performed in two separate frequency bands. Transmission and reception circuits need to be switched in transmission gaps between downlink and uplink transmissions and between downlink and uplink transmissions.
Frame structures having a CP length corresponding to ⅛ of an effective symbol length Tb for a channel bandwidth of 7 MHz, other than the basic frame structure of the IEEE 802.16m system, have yet to be suggested.